Technical Field
The present invention relates to wireless communication networks, and more particularly to routing signals through wireless networks.
Background
In some wireless communication systems, such as cellular communication systems, a geographic area of the network is broken up into sub-areas referred to as “cells.” Each cell may, for example, be about ten square miles in area in a larger area of 50 square miles. Each cell may include a device referred to as “base station,” which, in some systems, has a tower for receiving/transmitting and a base connected into a public switched telephone network (PSTN).
Areas are often divided into cells in order to use spectrum more efficiently. Typically, a wireless carrier is allocated a limited number of frequency channels. The use of the cells, in some applications, facilitates frequency reuse, such that, for instance, different users (e.g., individuals operating cellular handsets or devices that send or receive data over a wireless network) may communicate with different base stations over the same frequency in different cells, thereby re-using spectrum while avoiding or reducing interference. Cell phone systems are often digital with each cell having several channels for assignment to users. In a large city, there may be hundreds of cells.
Cellular networks often include a mobile telephone switching office (MSC) that, in some systems, controls certain aspects of the operation of some or all of the base stations in a region, control that may include control of the connections to a land-based PSTN. For instance, when a user's wireless device gets an incoming call, the MSC may attempt to locate in which cell the user's wireless device is located. The MSC then may instruct a base station and other system components to assigns resources for the call to the wireless device. The MSC then communicates with the user's wireless device over a control channel to inform the user's wireless device what resources to use. Typically, once the user's wireless device and its respective cell tower are connected, the call is on between the wireless device and tower. Similar mechanisms are used to facilitate data communication (e.g., packet switched data communication) between the wireless device and the network.
In some cellular communication systems, a wireless device directly communicates with the cellular base-station. That is, in some cellular wireless systems, the wireless device communicates with the cellular base-station via a single-hop, meaning that the signals sent between the wireless device and the base station are not mediated through an intermediary device that receives signals from one and passes them on to the other.
In some systems, at certain times, there may be a relatively large number of users attempting to directly communicate with the base-station in a cell. Some of these users may be located in areas referred to herein as “marginal-to-inoperative regions,” which are areas where the wireless service is spotty because the signal between the wireless device and the cellular base-station is weak or blocked, usually because of hilly terrain, excessive foliage, physical distances, concrete walls, or tall buildings. In another example of a marginal-to-inoperative region, some of these users may be located in areas referred to herein as “cell-edges,” which are areas where the interference from neighboring cells is relatively high.
Furthermore, the signal-quality (e.g., signal-strength, signal-to-noise ratio, signal-to-interference and noise ratio, or channel quality indicator) in some areas of the cell may not be strong enough to meet the throughput demand of the user. This is because when everything else is kept constant, the data rate that can be supported between a wireless device and a cellular base-station depends, in part, on the signal-strength or signal-quality between the device and the base-station. In some cellular systems, wireless devices are configured to transmit at a relatively high power when the device is in an area of the cell where the signal strength is low. This may help in supporting higher data rates between that particular device and that particular base-station. However, higher-power transmission may consume precious battery power of the device and also potentially causes more interference in the neighboring cells. Causing more interference in the neighboring cells may further hurt the effective capacity of the cellular system.
Some cellular systems may use adaptive modulation and coding. To facilitate communication, these systems often use modulation schemes and a certain amount of error correction coding (which, may tend to reduce the data rate or throughput of the wireless link) when the signal strength between a wireless device and the cellular base-station is relatively low. Thus, such systems may achieve a data rate between the device and the base-station that depends, in part, on the location of the device with respect to the base-station. Moreover, in these systems, if the same amount of spectrum was allocated to two similar wireless devices in a cell, where the signal-strength or signal-quality between the base-station and the first device is high and the signal-strength or signal-quality between the base-station and the second device is low, then the first device would (on average) be able to send/receive more useful data to/from the base-station. Thus, devices experiencing low signal-strength or signal-quality from the base-station may reduce the effective capacity of the wireless spectrum.
Therefore, there is a need in the art for expanding the effective coverage area and improving the effective capacity of cellular base-stations and cellular networks.